Theoretical study of oligomeric alumatranes present in the chemistry of materials from micro to mesoporous molecular sieves and alumina composites

Quantum chemical calculations using density functional theory have been carried out to investigate molecular precursors based on alumatranes which are one of the components with silatranes for the preparation of mesoporous aluminosilicate materials. In the same way, some oligomeric alumatranes of this study take part in chemical syntheses related to materials such as zeolites and alumina composite. Gas phase and solution equilibrium geometries of the alumatrane precursors were fully optimized at B3LYP level, modeling solvent effects using a self-consistent reaction field (SCRF). From these optimized geometries, calculations of the 1H, 13C and 27Al NMR chemical shifts at GIAO/B3LYP/6-31G(d,p) levels of theory have also been performed. This study has shown that the assumed conformations of the alumatrane precursors that have been derived from a previous work on a FAB-MASS analysis (Fast Atomic Bombardment Mass Spectroscopy) are confirmed by DFT calculations. All the conformations of alumatranes show that there would have transannular Al-N bond. Oligomeric alumatranes are composed of one or more two-membered Al2O2 rings where tricoordinated oxygen would be present. A good agreement between the experimental NMR data and the theoretical study on the chemical shifts of nucleus as 13C, 1H and 27Al from full geometry optimizations of the alumatrane precursors seems to corroborate the presence of the alumatrane precursors in the “atrane route”.